Gate stack and contact structure

ABSTRACT

A process for fabrication of semiconductor devices, particularly FinFETs, having a low contact horizontal resistance and a resulting device are provided. Embodiments include: providing a substrate having source and drain regions separated by a gate region; forming a gate electrode having a first length on the gate region; forming an epitaxy layer on the source and drain regions; forming a contact layer having a second length, longer than the first length, at least partially on the epitaxy layer; and forming an oxide layer on top and side surfaces of the contact layer for at least the first length.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Divisional of U.S. application Ser. No.14/147,181, filed Jan. 3, 2014, the content of which is incorporatedherein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to a manufacture of semiconductordevices, such as FinFETs. The present disclosure is particularlyapplicable to 10 nanometer (nm) technology nodes and beyond.

BACKGROUND

In a fabrication of semiconductor devices, many FinFETs rely on a tallgate structure. Such a structure may allow for a reduction in horizontalresistance. However, a tall gate structure typically results in highparasitic capacitance, and may require complex or costly metalchamfering and self-aligned contact (SAC) processes.

A need therefore exists for methodologies for fabrication ofsemiconductor devices, particularly FinFETs, having a low gatehorizontal resistance without use of a tall gate structure, and aresulting device.

SUMMARY

An aspect of the present disclosure is a method of providing a contactlayer having a length longer than a length of a gate electrode, at leastpartially on an epitaxy layer.

Another aspect of the present disclosure is a device including a contactlayer having a length longer than a length of a gate electrode, at leastpartially on an epitaxy layer.

Additional aspects and other features of the present disclosure will beset forth in the description which follows and in part will be apparentto those having ordinary skill in the art upon examination of thefollowing or may be learned from the practice of the present disclosure.The advantages of the present disclosure may be realized and obtained asparticularly pointed out in the appended claims.

According to the present disclosure, some technical effects may beachieved in part by a method including: providing a substrate havingsource and drain regions separated by a gate region; forming a gateelectrode having a first length on the gate region; forming an epitaxylayer on the source and drain regions; forming a contact layer having asecond length, longer than the first length, at least partially on theepitaxy layer; and forming an oxide layer on top and side surfaces ofthe contact layer for at least the first length.

Aspects include forming the gate electrode by: forming a polycrystallinesilicon gate on the gate region; forming a nitride layer on at leastside surfaces of the polycrystalline silicon gate; removing thepolycrystalline silicon gate to form a recess; forming a high-kdielectric in the recess; forming a metal gate on the high-k dielectricin the recess; and reducing a height of the metal gate; and forming asecond contact layer on the metal gate for the first length. Additionalaspects include: forming the nitride layer on side and top surfaces ofthe polycrystalline silicon gate; and removing the nitride from the topsurface prior to removing the polycrystalline silicon gate electrode.Further aspects include: forming the gate electrode by: forming a high-kdielectric layer in the gate region; forming a dummy gate on the high-kdielectric layer; annealing, prior to providing the oxide layer on thetop surface of the contact layer; removing the dummy gate to form arecess; forming a replacement metal gate on the high-k dielectric layerin the recess; and reducing a height of the metal gate; and providing asecond contact layer on the replacement metal gate for the first length.Additional aspects include a method, wherein the high-k dielectric is atside and bottom surfaces of the dummy gate, the method further includingforming a nitride layer on side surfaces of the high-k dielectric layer.Further aspects include: forming the first and second contact layers oftungsten (W); and forming the dummy gate of titanium nitride (TiN) andpolycrystalline silicon. Some aspects include: forming a low-kdielectric layer having first and second portions on the oxide layer inthe drain and source regions, respectively; and reducing a height of thegate electrode; and forming a second contact layer between the first andsecond portions of the low-k dielectric layer and on the gate electrode,extending over the drain and source regions over the first length, andbeing separated from the first contact layer by the oxide layer.Additional aspects include: forming a shallow trench isolation (STI)region in the substrate horizontally beyond the epitaxy layer, the firstcontact extending over the STI region; forming a vertical portion of thefirst contact layer over the STI region; and forming a second contactlayer on the gate electrode.

Another aspect of the present disclosure is a device including: asubstrate having source and drain regions separated by a gate region; agate electrode having a first length on the gate region; an epitaxylayer on the source and drain regions; a contact layer having a secondlength, longer than the first length, at least partially on the epitaxylayer; and an oxide layer on top and side surfaces of the contact layerfor at least the first length.

Some aspects include the gate electrode including: a metal gate; ahigh-k dielectric on side and bottom surfaces of the metal gate; anitride layer on side surfaces of the high-k dielectric; and a secondcontact layer on the metal gate for the first length. Additional aspectsinclude: the oxide layer separating the first and second contact layers;and the oxide and nitride layers separating the first contact layer andthe metal gate. Further aspects include: the metal gate and first andsecond contact layers including W; and the metal gate including a TiCwork function metal. Some aspects include: a low-k dielectric layerhaving first and second portions on the oxide layer in the drain andsource regions, respectively; and a second contact layer on the gateelectrode between the first and second portions of the low-k dielectriclayer, the second contact layer extending over the drain and sourceregions over the first length and being separated from the first contactlayer by the oxide layer. Further aspects include: a STI region in thesubstrate horizontally beyond the epitaxy layer, the first contactextending over the STI region; a vertical portion of the first contactlayer over the STI region; and a second contact layer on the gateregion. Some aspects include: a horizontal portion of the first contactlayer on the epitaxy layer having a thickness of 20 nm to 100 nm; and aportion of the second contact layer extending horizontally over thesource and drain regions having a thickness of 20 nm to 400 nm. Furtheraspects include a low-k dielectric layer separating the vertical portionof the first contact layer from the second contact layer.

Another aspect of the present disclosure is a method including:providing a substrate having source and drain regions separated by agate region; forming a gate electrode having a first horizontal lengthon the gate region and a first height; forming an epitaxy layer on thesource and drain regions; forming an STI region in the substratehorizontally beyond the epitaxy layer; forming a W contact layer havinga second horizontal length, longer than the first horizontal length, anda second height, less than the first height, at least partially on theepitaxy layer, the contact layer extending horizontally over the STIregion and including a vertical portion over the STI region; and formingan oxide layer on top and side surfaces of the contact layer for atleast the first length.

Some aspects include forming the gate electrode by: forming apolycrystalline silicon gate on the gate region; forming a nitride layeron side and top surfaces of the polycrystalline silicon gate; removingthe nitride from the top surface of the polycrystalline silicon gate;removing, after removal of the nitride from the top surface of thepolycrystalline silicon gate, the polycrystalline silicon gate to form arecess; forming a high-k dielectric in the recess; forming a TiC workfunction metal on the high-k dielectric in the recess; forming a metalgate on the work function metal in the recess; and reducing the heightof the metal gate to the first height; and forming a second contactlayer on the metal gate for the first horizontal length. Additionalaspects include forming the gate electrode by: forming a high-kdielectric layer in the gate region; forming a dummy gate on the high-kdielectric layer, the dummy gate including TiN and polycrystallinesilicon; annealing, prior to providing the oxide layer on the top andside surfaces of the first contact layer; removing the dummy gate toform a recess; forming a TiC work function metal layer in the recess;forming a replacement metal gate on the work function metal in therecess; reducing a height of the metal gate to the first height; andforming a W second contact layer on the metal gate for the first length;and forming a nitride layer on side surfaces of the high-k dielectriclayer. Further aspects include: forming a low-k dielectric layer havingfirst and second portions on the oxide layer in the drain and sourceregions, respectively; and forming a second contact layer on the gateelectrode and between the first and second portions of the low-kdielectric layer, extending over the drain and source regions over thefirst horizontal length, and being separated from the first contactlayer by the oxide layer.

Additional aspects and technical effects of the present disclosure willbecome readily apparent to those skilled in the art from the followingdetailed description wherein embodiments of the present disclosure aredescribed simply by way of illustration of the best mode contemplated tocarry out the present disclosure. As will be realized, the presentdisclosure is capable of other and different embodiments, and itsseveral details are capable of modifications in various obviousrespects, all without departing from the present disclosure.Accordingly, the drawings and description are to be regarded asillustrative in nature, and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawing and in whichlike reference numerals refer to similar elements and in which:

FIG. 1 illustrates a cross sectional view of a gate stack and contactstructure, in accordance with an exemplary embodiment;

FIG. 2 illustrates a first three-dimensional view of a gate stack andcontact structure, in accordance with an exemplary embodiment;

FIG. 3 illustrates a second three-dimensional view of a gate stack andcontact structure, in accordance with an exemplary embodiment;

FIG. 4 is a flowchart of a partial fabrication of semiconductor deviceshaving a low gate horizontal resistance, in accordance with an exemplaryembodiment;

FIGS. 5 through 10 illustrate a first method for partial fabrication ofsemiconductor devices having a low gate horizontal resistance, inaccordance with an exemplary embodiment;

FIGS. 11 through 15 illustrate a second method for partial fabricationof semiconductor devices having a low gate horizontal resistance, inaccordance with an exemplary embodiment;

FIG. 16 is a flowchart of steps for continuing fabrication ofsemiconductor devices having a low gate horizontal resistance, inaccordance with an exemplary embodiment; and

FIGS. 17 through 19 illustrate the steps for continuing fabrication ofsemiconductor devices having a low gate horizontal resistance, inaccordance with exemplary embodiments.

DETAILED DESCRIPTION

In the following description, for the purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of exemplary embodiments. It should be apparent, however,that exemplary embodiments may be practiced without these specificdetails or with an equivalent arrangement. In other instances,well-known structures and devices are shown in block diagram form inorder to avoid unnecessarily obscuring exemplary embodiments. Inaddition, unless otherwise indicated, all numbers expressing quantities,ratios, and numerical properties of ingredients, reaction conditions,and so forth used in the specification and claims are to be understoodas being modified in all instances by the term “about.”

The present disclosure addresses and solves the current problems of highgate horizontal resistance or complex metal chamfering and SAC processesattendant upon fabricating FinFET gate and source/drain contactstructures at 10 nm technology nodes and beyond. The problems aresolved, for instance, by providing a source/drain contact layer having alength longer than a length of a gate electrode, and a vertical portionbeyond the gate electrode.

Methodology in accordance with embodiments of the present disclosureincludes: providing a substrate having source and drain regionsseparated by a gate region; forming a gate electrode having a firstlength on the gate region; forming an epitaxy layer on the source anddrain regions; forming a contact layer having a second length, longerthan the first length, at least partially on the epitaxy layer; andforming an oxide layer on top and side surfaces of the contact layer forat least the first length.

FIG. 1 includes a device 100 having a (bulk silicon) substrate 101 withsource and drain regions 103 and 105, respectively separated by gateregion 107. The gate region 107 includes a gate stack 109 and the sourceand drain regions 103 and 105 include an epitaxy layer 111, contactlayer 113 (e.g., W), and oxide layer 115. As shown, a horizontal portionof the contact layer 113 has a thickness of 20 nm to 100 nm.

The gate stack 109 may include metal gate 117, high-k dielectric 119(e.g., a material having a relative dielectric constant value greaterthan 3.9), and work function metal 121 (e.g., TiC). A gate contact layer125 (e.g., W) is formed over the gate stack 109. As shown, the gatecontact layer 125 extends over source and drain regions 103 and 105,resulting in a wide horizontal region that reduces a gate resistance andallows for manufacturing variances in landing the gate contact layer 125onto the gate stack 109. Moreover, the device 100 separates the gatecontact layer 125 and the contact layer 113, resulting in a lowparasitic capacitance compared to traditional methods. A nitride layer123 is formed around high-k dielectric 119. As shown, the oxide layer115 separates the contact layers 113 and 125 and the oxide and nitridelayers 115 and 123, respectively, separate the contact layer 113 and themetal gate 117. Additionally, the gate contact layer 125 has a portionextending horizontally over the source and drain regions 103 and 105,respectively, having a thickness of 20 nm to 400 nm.

Additionally, the device 100 further includes a low-k dielectric layer127 (e.g., a material having a relative dielectric constant value lessthan 3.9) having first and second portions on the oxide layer 115 in thesource and drain regions 103 and 105, respectively, and the gate contactlayer 125 is between the first and second portions of the low-kdielectric layer 127. As shown, the gate contact layer 125 extends overedges of the source and drain regions 103 and 105, respectively.

FIG. 2 illustrates the epitaxy layer 111 and gate contact layer 125extending a first horizontal distance 201 and the contact layer 113extending a second horizontal distance 203, longer than the firsthorizontal distance, into a STI region 205 of substrate 101. As shown,the contact layer 113 includes a vertical portion 207 (e.g., contactlanding portion) over the STI region 205 that is landed onto the contactlayer 113 (e.g., buried contact). FIG. 3 illustrates the low-kdielectric layer 127 separating the vertical portion 207 of the contactlayer 113 from the gate contact layer 125.

FIG. 4 is a flowchart of a process 400 for partial fabrication ofsemiconductor devices having a low gate horizontal resistance, accordingto an exemplary embodiment. The process of FIG. 4 is discussed withrespect to a first method illustrated in FIGS. 5 through 10 and a secondmethod illustrated in FIGS. 11 through 15.

In step 401, the process 400 provides a gate electrode having a firstlength on a gate region between source and drain regions. As illustratedin FIG. 5, source and drain regions 501 and 503, respectively, having anepitaxy layer 505 are separated by a gate region 507 having a gate stack509. The gate stack 509 extends for a first horizontal distance 201 (asillustrated in FIG. 2). The gate stack 509 may, for instance, be formedas a dummy gate 513 of polycrystalline silicon. A nitride layer 515surrounds gate stack 509 on side and top surfaces. An oxide layer 517may be formed on epitaxy layer 505 adjacent side surfaces of the nitridelayer 515.

Adverting to FIG. 6, a contact layer 601 (e.g., W) is formed, as in step403, having a length 203 (as shown if FIG. 2) on source and drainregions 501 and 503, respectively. The nitride layer 515 may act as aSAC layer during an etching process for the contact layer 601. Thelength of contact layer 601 is longer than the length of gate stack 509,but contact layer 601 is formed on the epitaxy layer 505 for the lengthof the gate electrode. The process 400 may optionally include a polishon chip, and chemical-mechanical planarization (CMP) after forming thecontact layer 601.

Adverting to FIG. 7, a reactive-ion etching (RIE) is performed to reducethe contact layer 601 to, for instance, a thickness of 20 nm to 100 nm.As illustrated in FIG. 8, an oxide layer 801 is then formed, as in step405, over the contact layer 601. The oxide layer 801 is on top and sidesurfaces of the contact layer 601 for the length of the gate stack 109.

Adverting to FIG. 9, the polycrystalline silicon dummy gate 513 isremoved to form a recess 901. The process may include, for instance, aRIE and a chemical washing. As shown, a high-k dielectric 903 isdeposited in the recess. As shown in FIG. 10, a work function metal 1001(e.g., TiC)) is formed on the high-k dielectric 903 and a metal gate1003 (e.g., W) is formed on the work function metal 1001.

As noted above, a second method illustrating the process of FIG. 4 isillustrated in FIGS. 11 through 15.

In step 401, the process 400 provides a gate electrode having a firstlength on a gate region. As illustrated in FIG. 11, source and drainregions 1101 and 1103, respectively, having an epitaxy layer 1105 areseparated by a gate region 1107 having a gate electrode 1109. The gateelectrode 1109 may, for instance, be a dummy gate (e.g., TiN andpolycrystalline silicon) with a high-k dielectric layer 1115 on side andbottom surfaces thereof. A nitride layer 1117 may be formed at sidesurfaces of high-k dielectric layer 1115. An oxide layer 1119 may beformed on epitaxy layer 1105 adjacent side surfaces of the nitride layer1117. An annealing process is then performed.

Adverting to FIG. 12, a contact layer 1201 (e.g., W) is formed, as instep 403, on epitaxy layer 1105 over source and drain regions 1101 and1103. The length of contact layer 1201 is longer than a length of thegate electrode 1109. The process 400 may optionally include a polish onchip and CMP after formation of the contact layer 1201. Similarly toFIG. 7, a RIE may be performed to reduce the contact layer 1201 to, forinstance, a thickness of 20 nm to 100 nm.

Adverting to FIG. 13, an oxide layer 1301 is formed, as in step 405, ontop and side surfaces of the contact layer 1201 for the length of thegate electrode.

Adverting to FIG. 14, the dummy gate of the gate electrode 1109 isremoved to form a recess 1401. As shown in FIG. 15, a work functionmetal layer 1501 (e.g., TiC) is provided on the high-k dielectric layer1115 and a replacement metal gate 1503 (e.g., W) is provided on the workfunction metal layer 1501.

FIG. 16 is a flowchart of a process for continuing fabrication ofsemiconductor devices having a low gate horizontal resistance, accordingto an exemplary embodiment. The process of FIG. 16 is discussed withrespect to FIGS. 17 through 19, and being after the metal gate 1003 or1503 is formed, according to methods illustrated in FIGS. 5 through 10and FIGS. 11 through 15, respectively.

Adverting to FIG. 17, source and drain regions 1701 and 1703,respectively, each having a contact layer 1705 separated by a gateregion 1707 having a gate electrode 1709. A low-k dielectric layer 1711is deposited over the top surface of source and drain regions 1701 and1703, respectively, and gate electrode 1709. The process may optionallyinclude a CMP after forming the low-k dielectric layer 1711.

Adverting to FIG. 18, a litho-etch step is performed to remove portionsof the low-k dielectric layer 1711 extending over the gate region 1707and edges of regions 1701 and 1703, resulting in recesses 1801. Duringthe litho etch step, gate electrode 1709 is reduced in height (not shownfor illustrative convenience). Next, as illustrated in FIG. 19, gatecontacts 1901 are deposited in the recesses 1801. The gate contacts 1901extend over edges of the source and drain regions 1701 and 1703,respectively. CMP is performed after providing the gate contacts 1901.

Additionally, the steps illustrated in FIGS. 4 through 19 may furtherinclude a litho-etch step to open a low-k dielectric layer (e.g., 127)for forming vertical portions (e.g., contact landing portions) to landon buried contacts (e.g., W), such as, for instance, 113, 601, 1201,1705.

The embodiments of the present disclosure achieve several technicaleffects, including fabrication of semiconductor devices, particularlyFinFETs, having a low gate horizontal resistance without use of a tallgate structure, and a resulting device. Embodiments of the presentdisclosure enjoy utility in various industrial applications as, forexample, microprocessors, smart phones, mobile phones, cellularhandsets, set-top boxes, DVD recorders and players, automotivenavigation, printers and peripherals, networking and telecom equipment,gaming systems, and digital cameras. The present disclosure thereforeenjoys industrial applicability in any of various types of highlyintegrated semiconductor devices, particularly at 10 nm technology nodesand beyond.

In the preceding description, the present disclosure is described withreference to specifically exemplary embodiments thereof. It will,however, be evident that various modifications and changes may be madethereto without departing from the broader spirit and scope of thepresent disclosure, as set forth in the claims. The specification anddrawings are, accordingly, to be regarded as illustrative and not asrestrictive. It is understood that the present disclosure is capable ofusing various other combinations and embodiments and is capable of anychanges or modifications within the scope of the inventive concept asexpressed herein.

What is claimed is:
 1. A device comprising: a substrate having a sourceregion and a drain region separated along a first direction by a gateregion, a thickness of the substrate defining a thickness direction; agate electrode having a first maximum length, along a second direction,the gate electrode being on the gate region, the second direction beingperpendicular to both the first direction and the thickness direction;an epitaxy layer on the source region and the drain region; a firstcontact layer having a second maximum length along the second direction,the second maximum length being longer than the first maximum length,the first contact layer being at least partially on the epitaxy layer;and an oxide layer on a top surface and side surfaces of the firstcontact layer for at least the first maximum length.
 2. The deviceaccording to claim 1, wherein the gate electrode comprises: a metalgate; a high-k dielectric on side surfaceas and a bottom surface of themetal gate; a nitride layer on side surfaces of the high-k dielectric;and a second contact layer on the metal gate for the first maximumlength.
 3. The device according to claim 2, wherein: the oxide layerseparates the first contact layer and the second contact layer; and theoxide layer and the nitride layer separate the first contact layer andthe metal gate.
 4. The device according to claim 2, wherein: the metalgate, the first contact layer and the second contact layer each comprisetungsten (W); and the metal gate comprises a titanium carbide (TiC) workfunction metal.
 5. The device according to claim 4, further comprising:a low-k dielectric layer having a first and a second portion over thedrain region and the source region, respectively, the first portion andthe second portion of the low-k dielectric layer being on the oxidelayer, wherein the second contact layer is disposed on the gateelectrode and between the first portion and the second portion of thelow-k dielectric layer, the second contact layer extending over thedrain region and the source region over the first maximum length andbeing separated from the first contact layer by the oxide layer.
 6. Thedevice according to claim 1, further comprising: a shallow trenchisolation (STI) region in the substrate horizontally beyond the epitaxylayer, the first contact layer extending over the STI region; a verticalportion of the first contact layer over the STI region; and a secondcontact layer on the gate region.
 7. The device according to claim 6,further comprising: a horizontal portion of the first contact layer onthe epitaxy layer and having a thickness of 20 nanometers (nm) to 100nm; and a portion of the second contact layer extending horizontallyover the source region and drain region and having a thickness of 20 nmto 400 nm.
 8. The device according to claim 6, further comprising: alow-k dielectric layer separating the vertical portion of the firstcontact layer from the second contact layer.
 9. A device comprising: asubstrate having a source region and a drain region separated along afirst direction by a gate region, a thickness of the substrate defininga thickness direction; a gate electrode having a first maximumhorizontal length along a second direction, the gate electrode being onthe gate region and having a first height, the second direction beingperpendicular to both the first direction and the thickness direction;an epitaxy layer on the source region and the drain region; a shallowtrench isolation (STI) region in the substrate horizontally beyond theepitaxy layer; a tungsten (W) contact layer having a second maximumhorizontal length along the second direction, the second maximumhorizontal length being longer than the first maximum horizontal length,the tungsten contact layer having a second height less than the firstheight and being at least partially on the epitaxy layer, the tunstencontact layer extending horizontally over the STI region and comprisinga vertical portion over the STI region, the tungsten contact layer beinga first contact layer; and an oxide layer on a top surface and sidesurfaces of the first contact layer for at least the first maximumhorizontal length.
 10. The device according to claim 9, wherein the gateelectrode comprises: a metal gate; a high-k dielectric on side surfacesand a bottom surface of the metal gate; a nitride layer on side surfacesof the high-k dielectric; and a second contact layer on the metal gatefor the first maximum horizontal length.
 11. The device according toclaim 10, wherein: the oxide layer separates the first contact layer andthe second contact layer; and the oxide layer and the nitride layerseparate the first contact layer and the metal gate.
 12. The deviceaccording to claim 9, further comprising: a low-k dielectric layerhaving a first portion and a second portion over the drain region andthe source region, respectively, the first portion and the secondportion of the low-k dielectric layer being on the oxide layer; and asecond contact layer on the gate electrode and between the first portionand The second portion of the low-k dielectric layer, the second contactlayer extending over the drain region and the source region over thefirst maximum horizontal length and being separated from the firstcontact layer by the oxide layer.